Here a new, intrinsically pluripotent, CD45-negative population from human cord blood, termed unrestricted somatic stem cells (USSCs) is described. This rare population grows adherently and can be expanded to 1015 cells without losing pluripotency. In vitro USSCs showed homogeneous differentiation into osteoblasts, chondroblasts, adipocytes, and hematopoietic and neural cells including astrocytes and neurons that express neurofilament, sodium channel protein, and various neurotransmitter phenotypes. Stereotactic implantation of USSCs into intact adult rat brain revealed that human Tau-positive cells persisted for up to 3 mo and showed migratory activity and a typical neuron-like morphology. In vivo differentiation of USSCs along mesodermal and endodermal pathways was demonstrated in animal models. Bony reconstitution was observed after transplantation of USSC-loaded calcium phosphate cylinders in nude rat femurs. Chondrogenesis occurred after transplanting cell-loaded gelfoam sponges into nude mice. Transplantation of USSCs in a noninjury model, the preimmune fetal sheep, resulted in up to 5% human hematopoietic engraftment. More than 20% albumin-producing human parenchymal hepatic cells with absence of cell fusion and substantial numbers of human cardiomyocytes in both atria and ventricles of the sheep heart were detected many months after USSC transplantation. No tumor formation was observed in any of these animals.

Background Human cardiac progenitor cells (hCPCs) may promote myocardial regeneration in adult ischemic myocardium. The regenerative capacity of hCPCs in young patients with nonischemic congenital heart defects for potential use in congenital heart defect repair warrants exploration. Methods and Results Human right atrial specimens were obtained during routine congenital cardiac surgery across 3 groups: neonates (age, <30 days), infants (age, 1 month to 2 years), and children (age, >2 to ≤13 years). C-kit+ hCPCs were 3-fold higher in neonates than in children >2 years of age. hCPC proliferation was greatest during the neonatal period as evidenced by c-kit+ Ki67+ expression but decreased with age. hCPC differentiation capacity was also greatest in neonatal right atrium as evidenced by c-kit+, NKX2–5+, NOTCH1+, and NUMB+ expression. Despite the age-dependent decline in resident hCPCs, we isolated and expanded right atrium–derived CPCs from all patients (n = 103) across all ages and diagnoses using the cardiosphere method. Intact cardiospheres contained a mix of heart-derived cell subpopulations that included cardiac progenitor cells expressing c-kit+, Islet-1, and supporting cells. The number of c-kit+–expressing cells was highest in human cardiosphere-derived cells (hCDCs) grown from neonatal and infant right atrium. Furthermore, hCDCs could differentiate into diverse cardiovascular lineages by in vitro differentiation assays. Transplanted hCDCs promoted greater myocardial regeneration and functional improvement in infarcted myocardium than transplanted cardiac fibroblasts. Conclusions Resident hCPCs are most abundant in the neonatal period and rapidly decrease over time. hCDCs can be reproducibly isolated and expanded from young human myocardial samples regardless of age or diagnosis. hCPCs are functional and have potential in congenital cardiac repair.

Alternative methods to whole liver transplantation require a suitable cell that can be expanded to obtain sufficient numbers required for successful transplantation while maintaining the ability to differentiate into hepatocytes. Mesenchymal stem cells (MSCs) possess several advantageous characteristics for cell-based therapy and have been shown to be able to differentiate into hepatocytes. Thus, we investigated whether the intrahepatic delivery of human MSCs is a safe and effective method for generating human hepatocytes and whether the route of administration influences the levels of donorderived hepatocytes and their pattern of distribution throughout the parenchyma of the recipient's liver. Human clonally derived MSCs were transplanted by an intraperitoneal (n ‫؍‬ 6) or intrahepatic (n ‫؍‬ 6) route into preimmune fetal sheep. The animals were analyzed 56-70 days after transplantation by immunohistochemistry, enzyme-linked immunosorbent assay, and flow cytometry. The intrahepatic injection of human MSCs was safe and resulted in more efficient generation of hepatocytes (12.5% ؎ 3.5% versus 2.6% ؎ 0.4%). The animals that received an intrahepatic injection exhibited a widespread distribution of hepatocytes throughout the liver parenchyma, whereas an intraperitoneal injection resulted in a preferential periportal distribution of human hepatocytes that produced higher amounts of albumin. Furthermore, hepatocytes were generated from MSCs without the need to first migrate/lodge to the bone marrow and give rise to hematopoietic cells. Conclusion: Our studies provide evidence that MSCs are a valuable source of cells for liver repair and regeneration and that, by the alteration of the site of injection, the generation of hepatocytes occurs in different hepatic zones, suggesting that a combined transplantation approach may be necessary to successfully repopulate the liver with these cells. (HEPATOLOGY 2007;46:1935-1945 T he maintenance of cellular homeostasis within the normal liver and during liver regeneration is provided by mature hepatocytes and cholangiocytes and by the intrahepatic (IH) stem cell compartment located in the canals of Hering and the intralobular bile ducts. 1 Recently, another potential source of cells able to provide liver cell replacement has been identified. These stem/progenitor cells consist of hematopoietic stem cells (HSCs) and mesenchymal stem cells (MSCs) that reside within the bone marrow (BM) but can reach the liver through the circulatory system. [2][3][4][5][6][7][8][9][10][11][12] Because it is clearly evident that the shortage of available human donor organs cannot meet the needs of all the patients awaiting liver transplantation, alternatives to whole-organ replacement are urgently needed. Cell-based treatments, with cells of either hepatic or extrahepatic origin that would be able to repopulate and re-establish a functional liver after administration, could serve as a possible alternative to wholeorgan transplantation.In order to attain this goal, several questions, such as the sour...